Injuries to the anterior cruciate ligament (ACL) are a common occurrence. Though mild ACL injuries may be treated non-surgically, completely ruptured ACLs typically require surgical reconstruction. See generally American Academy of Orthopaedic Surgeons, ACL Injury: Does it Require Surgery?, OrthoInfo (September 2009), https://orthoinfo.aaos.org/en/treatment/acl-injury-does-it-require-surgery [AAOS, OrthoInfo (September 2009)]. Surgically repaired ACLs have a high rate of failure, and thus the damaged ACL is usually removed and replaced by a substitute graft during surgery. [AAOS, OrthoInfo (September 2009)] Current reconstructive techniques involve placing and securing a graft so as to recreate the biomechanical properties of the original ligament. See, e.g., Brian C. Werner et al., A Prospective Evaluation of the Anterior Horn of the Lateral Meniscus as a Landmark for Tibial Tunnel Placement in Anterior Cruciate Ligament (ACL) Reconstruction, 23 The Knee 478 (2016). During a typical reconstructive procedure, bone tunnels are drilled into the femur and tibia in order to receive and secure the graft. Sebastián Irarrázaval et al., Anterior Cruciate Ligament Reconstruction, 1 J. ISAKOS 38 (2016). Common graft options include hamstring tendon autographs, bone-patellar tendon-bone autografts, quadricep tendon autografts, and allografts. Irarrázaval et al. After the graft is pulled through the drilled bone tunnels, devices such as bone plugs, metal screws, or bio-interference screws are typically employed to securely fix the graft to the femur and tibia. Irarrázaval et al.
Improper positioning of the femoral or tibial tunnel are the most commonly cited reasons for graft failure. Werner et al. There is no consensus regarding the most effective position or orientation of the femoral tunnel. Werner et al. For example, vertically oriented femoral tunnels have been associated with an inability to control rotational forces across the surgically repaired knee. Werner et al. Studies suggest that horizontally oriented femoral tunnels placed independently of tibial tunnels may mitigate the drawbacks associated with vertically oriented femoral tunnels. Werner et al. However, there is currently no efficient manner in identifying the most effective position and orientation of the femoral tunnel. Werner et al.
The proper location of the tibial tunnel is also disputed. Werner et al. Variation in tibial tunnel placement can have detrimental effects on the success of the reconstructive procedure and the long-term prognosis for the surgically repaired knee. Werner et al. Studies suggest that placement of the tibial tunnel too posterior across the tibial plateau results in diminished knee stability. Conversely, a placement too anterior can result in graft impingement during knee extension. Werner et al. Historically, the recommended location for the tibial tunnel was in the center of the anatomic tibial footprint. Werner et al.
Certain techniques involve placing the tibial tunnel in reference to one or more intra-articular anatomic landmarks. For example, Kassam et al. describe a technique in which the tibial tunnel is placed in reference to the posterior border of the anterior horn of the lateral meniscus. Al-Amin M. Kassam et al., Anatomic Anterior Cruciate Ligament Reconstruction: The Use of the Anterior of the Lateral Meniscus as a Guide to Tibial Tunnel Placement, 5 Arthroscopy Techniques 809 (2016). Parsons' knob and the medial intercondylar ridge have also been described as bony landmarks to define a reference boundary to aid in positioning the tibial tunnel. Hiroki Shimodaira et al., Tibial Tunnel Positioning Technique Using Bony/Anatomical Landmarks in Anatomical Anterior Cruciate Ligament Reconstruction, 6 Arthroscopy Techniques 49 (2017). Additionally, the posterior cruciate ligament (PCL) is a commonly referenced anatomic landmark. For example, Burnham et al. recommend placing the tibial tunnel fifteen millimeters anterior to the PCL, in line with the posterior edge of the anterior horn of the lateral meniscus. Jeremy M. Burnham et al., Anatomic Femoral and Tibial Tunnel Placement During Anterior Cruciate Ligament Reconstruction: Anteromedial Portal All-Inside and Outside-In Techniques, 6 Arthroscopy Techniques 275 (2017). Zantop et al. and Morgan et al. likewise describe the proper tibial tunnel location in reference to an anterior displacement from the PCL. Thore Zantop et al., Tunnel Positioning of Anteromedial and Posterolateral Bundles in Anatomic Anterior Cruciate Ligament Reconstruction, 36 Am. J. Sports Med. 65 (2008); Craig D. Morgan et al., Definitive Landmarks for Reproducible Tibial Tunnel Placement in Anterior Cruciate Ligament Reconstruction, 11 J. Arthroscopic and Related Surgery 275 (1995). It should be appreciated that there is a lack of consensus in these approaches, particularly in terms of the magnitude of displacement from the referenced anatomic structures.
Other approaches seek to incidentally place the tibial tunnel in the center of the anatomic tibial footprint as defined by radiographic measurements. Werner et al. (citing H. U. Staubli & W. Rauschning, Tibial Attachment Area of the Anterior Cruciate Ligament in the Extended Knee Position—Anatomy and Cryosections In Vitro Complemented by Magnetic Resonance Arthrography In Vivo, 2 Knee Surgery, Sports Traumatology, Arthroscopy 138 (1994)). Many surgeons believed that placing the tibial tunnel in reference to intra-articular landmarks would result in a tibial tunnel location closely corresponding to the center of the anatomic tibial footprint as defined by radiographic measurements. Werner et al. However, recent research indicates that placing the tibial tunnel in reference to intra-articular landmarks, such as the lateral meniscus, results in inconsistent tibial tunnel locations and a variance of tibial tunnel locations relative to the center of the anatomic tibial footprint. Werner et al. In particular, placing the tibial tunnel in reference to the lateral meniscus has been demonstrated to result in an average tibial tunnel location anterior to the center of the anatomic tibial footprint. Werner et al. As discussed, among other drawbacks, this may increase the risk of graft impingement during knee extension. Werner et al.
The present inventor notes, as disclosed herein pertaining to embodiments of the present invention, that it is useful to place the tibial tunnel at a predefined percentage across the anterior-posterior distance of the tibial plateau. This approach will account for, among other things, differences in individual patient anatomy, improve technique reproducibility, and mitigate the risks herein discussed associated with tunnel malpositioning.
Some currently available devices, such as those disclosed in U.S. Pat. Nos. 5,269,786, 5,409,494, and 5,562,664 to Morgan et al., reference the PCL as an anatomic landmark and place the tibial tunnel at a fixed distance anterior to the leading edge of the PCL. Other devices, such as those disclosed by Howell in U.S. Pat. No. 6,254,605, mention landmarks to place the tibial tunnel in reference thereto. Similarly, other devices, such as those disclosed by Paulos in U.S. patent application Ser. No. 13/292,062 (U.S. Patent Application Publication No. US2012/0059382 A1), describe devices that may hook to a posterior region of a tibial plateau and provide apertures to drill a tibial tunnel at predetermined and fixed distances in reference thereto. Still others may allow a user to provide a tibial bone tunnel in reference to a first drilled femoral tunnel, as disclosed in U.S. Pat. No. 8,298,239 to Re, or at an offset from a first drilled bone tunnel, as disclosed in U.S. Pat. No. 7,736,364 to Stone. Other devices, such as the Acufex Director from Smith & Nephew are capable of placing a tibial tunnel on a tibial plateau (such as an anatomic landmark), but these devices lack the capability of measuring the tibial plateau and engaging the tibial plateau at a precise target distance. A description of the Acufex Director is available at http://www.smith-nephew.com/professional/products/all-products/acufex-director/. The aforementioned disclosures are herein incorporated by reference in their entirety.
No currently available device allows a user to measure the total distance across a tibial plateau and engage the tibial plateau at a precise target distance across the tibial plateau based upon a predetermined target percentage across the anterior-posterior distance of the tibial plateau. Moreover, no device provides this important advantage in a reproducible and consistent manner without the use of fluoroscopy or other imaging techniques.